The reflective liquid crystal projector is mainly constituted of a light source, a color separating optical element such as a dichroic mirror or a dichroic prism, polarizing beam splitter prisms, hereinafter called briefly the PBS prisms, three liquid crystal elements, a recombination prism, and a projection lens. White light from the light source is separated into a blue illumination beam, a red illumination beam and a green illumination beam. The liquid crystal elements modulate and reflect the three color illumination beams respectively, to produce three color optical images. The three color optical images are combined together through the recombination prism, and the combined full-color image is projected through the projection lens onto a screen.
In conventional liquid crystal projectors, the recombination prism is held in a predetermined position by a prism holder, as disclosed in Japanese laid-open Patent Application No. 2001-42425. The recombination prism is a rectangular prism, and the prism holder is formed with mounting portions which top and bottom surfaces of the rectangular prism adhere to. The mounting portions are provided with holes for accepting an adhesive agent. After the top and bottom surfaces of the recombination prism are brought into contact with the mounting portions, the adhesive agent is poured into the holes, so that the top and bottom surfaces of the recombination prism are fixed to the mounting portions.
In the reflective liquid crystal projector, the PBS prisms are used for separating illumination light paths from image light paths. The PBS prism is conventionally held by bonding top and bottom sides of the prism to respective prism holders with the adhesive agent. Because of thermal swelling of the prism holders, which is caused while the liquid crystal projector is being used, the PBS prism leans to distort the image projected on the screen, deteriorating the image quality. Since the prism holders are bonded to the top and bottom surfaces of the PBS prism, the total size of the liquid crystal projector is enlarged by the mounting space of the prism holders.